Lubricating system for power unit for vehicle with internal combustion engine

ABSTRACT

A lubricating system for a power unit for a vehicle with an internal combustion engine. A static oil hydraulic type non-stage transmission is disposed on a left lateral side of a crankshaft, and a lubricating oil tank is formed integrally with a main body of the internal combustion engine and is disposed on a right lateral side opposite to the side of the transmission, with the crankshaft therebetween.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a lubricating system in a powerunit for a vehicle with an internal combustion engine by which the powerof an internal combustion engine having a crankshaft directed in thefront-rear direction of the vehicle is transmitted to wheels through astatic oil hydraulic type non-stage transmission.

[0003] 2. Description of the Related Art

[0004] There has been known a lubricating system for a power unit for avehicle with an internal combustion engine in which a static oilhydraulic type non-stage transmission comprised of a swash plate typeoil hydraulic pump and a swash plate type oil hydraulic motor isincorporated integrally with an internal combustion engine, wherein alubricating oil tank is integrally mounted to the front surface of acase of the power unit. The lubricating oil flowing down to a bottomportion of the space inside the power unit is sucked up by a recoverypump, and is charged into the lubricating oil tank. The lubricating oilin the lubricating oil tank is supplied to the portions to be lubricatedof the internal combustion engine and to the static oil hydraulic typenon-stage transmission by a supply pump. An example of such alubricating system is disclosed in Japanese Patent Laid-open No.2001-343060.

[0005] In the above-mentioned lubricating system for the power unit fora vehicle with an internal combustion engine, the lubricating oil tankis separate from the power unit and is integrally mounted to the outsidesurface of the power unit. Therefore, the number of component parts isincreased, which also increases costs.

[0006] In addition, since the static oil hydraulic type non-stagetransmission is relatively large in weight and is disposed on either oneof the left and right sides of the crankshaft of the internal combustionengine, in order to establish the proper balance between the left sideand the right side of the vehicle body it has been necessary to takeinto account the conditions of arrangement of various shafts in thepower unit and the conditions of arrangement of various component parts.

[0007] The present invention pertains to a lubricating system for apower unit for vehicle with internal combustion engine, and has beenmade for solving the problems in the above-mentioned prior art.

SUMMARY OF THE INVENTION

[0008] In one aspect of the present invention, a lubricating system fora power unit for a vehicle with an internal combustion engine isprovided. The system includes an internal combustion engine having acrankshaft directed in the front-rear direction of a vehicle body, astatic oil hydraulic non-stage transmission having a swash plate oilhydraulic pump and a swash plate oil hydraulic motor, and a lubricatingoil tank for a lubricating oil to be supplied to individual portions ofthe internal combustion engine and to the transmission. The transmissionis disposed on either one of the left and right sides of the crankshaft,and the lubricating oil tank is formed integrally with a main body ofthe power unit for vehicle or a main body of the internal combustionengine and is disposed on a lateral side opposite to the side of thestatic oil hydraulic type non-stage transmission, with the crankshafttherebetween.

[0009] In another aspect of the present invention, a power unit for avehicle with an internal combustion engine is provided. The systemcomprises an internal combustion engine having a crankshaft directed ina front-rear direction of a vehicle body; a static oil hydraulicnon-stage transmission comprised of a swash plate oil hydraulic pump anda swash plate oil hydraulic motor; and tank means for holding alubricating oil to be supplied to individual portions of the internalcombustion engine and to the transmission. The transmission is disposedon either the left or right side of the crankshaft, and the tank meansis formed integrally with a main body of the power unit and is disposedon a lateral side of the crankshaft that is opposite to the side onwhich the transmission is disposed.

[0010] Thus, the static oil hydraulic type non-stage transmission isdisposed on either one of the left and right sides of the crankshaftdirected in the front-rear direction of the vehicle, and the lubricatingoil tank is disposed on the other of the left and right sides of thecrankshaft. Therefore, even if the static oil hydraulic type non-stagetransmission is comparatively large in weight, the weight balancebetween the left side and the right side of the power unit for vehiclewith internal combustion engine can be easily taken by utilizing theweight of the lubricating oil tank and the weight of the lubricating oilcharged in the lubricating oil tank.

[0011] Moreover, since the lubricating oil tank is formed integrallywith the main body of the power unit for vehicle or the main body of theinternal combustion engine, the lubricating oil tank is firmly connectedto the main body, and the number of component parts is largely reduced,whereby reductions in cost and weight and an enlargement of the tankcapacity can be realized.

[0012] In another aspect of the present invention, the lubricating tankis not only constituted by the crankcase for bearing the crankshaft butalso constituted by the crankcase cover making contact with an outsidesurface of the crankcase and covering the outside surface of thecrankcase, so that a further enlargement of the capacity of thelubricating oil tank can be achieved.

[0013] Moreover, since the crankcase and the crankcase cover can both beeasily die-cast or cast, a further enhancement of productivity and afurther reduction in cost can be achieved.

[0014] In yet another aspect of the present invention, a recovery pumpby which a lubricating oil dropping to a bottom portion of the inside ofthe crankcase is returned to the lubricating oil tank and a supply pumpfor supplying the lubricating oil from the lubricating oil tank toindividual portions of the internal combustion engine and to the staticoil hydraulic type non-stage transmission are disposed coaxially.Therefore, the overall size of a lubricating oil pump comprised of bothof the pumps is reduced, whereby the lubricating oil pump can be reducedin weight and size, and an oil passage between the lubricating oil pumpsand an oil passage between the lubricating oil pump and the lubricatingoil tank are shortened, thereby decreasing pump losses.

[0015] In another aspect of the present invention, an oil filter forfiltering the lubricating oil to be supplied from the lubricating oiltank to individual portions of the internal combustion engine and to thestatic oil hydraulic type non-stage transmission is disposed at aposition on the front side of the lubricating oil tank and overlappingwith the lubricating oil tank as viewed forwards with respect to thevehicle, so that the lubricating oil tank and the oil filter are closeto each other. Therefore, the oil relieved from the filter isimmediately fed back into the lubricating oil tank, and, since the oilfilter is close to the lubricating oil pump, pump losses can be isreduced.

[0016] Moreover, since the oil filter is located on the front side ofthe power unit, maintenance, inspection and repair of the oil filter canbe carried out simply and easily.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a side view of a vehicle on which a power unit accordingto the present invention is mounted.

[0018]FIG. 2 is a front view, as viewed from the front side, of thepower unit shown in FIG. 1.

[0019]FIG. 3 is a cross-sectional view of the power unit for vehiclewith internal combustion engine, taken along line III-III of FIG. 1.

[0020]FIG. 4 is a vertical sectional view of the power unit for vehiclewith internal combustion engine shown in FIG. 1.

[0021]FIG. 5 is a vertical sectional view of a static oil hydraulic typenon-stage transmission of the present invention.

[0022]FIG. 6 is a front view of a front case cover of the presentinvention.

[0023]FIG. 7 is a front view of a front crankcase of the presentinvention.

[0024]FIG. 8 is a rear view of the front crankcase of the presentinvention.

[0025]FIG. 9 is a front view of a rear crankcase of the presentinvention.

[0026]FIG. 10 is a rear view of the rear crankcase of the presentinvention.

[0027]FIG. 11 is a front view of a rear case cover of the presentinvention.

[0028]FIG. 12 is a rear view of the rear case cover of the presentinvention.

[0029]FIG. 13 is a plan view of the front crankcase and the rearcrankcase of the present invention.

[0030]FIG. 14 is a sectional view taken along line XIV-XIV of FIG. 6.

[0031]FIG. 15 is a sectional view taken along line XV-XV of FIG. 6.

[0032]FIG. 16 is a sectional view taken along line XVI-XVI of FIG. 6.

[0033]FIG. 17 is a sectional view taken along line XVII-XVII of FIG. 6.

[0034]FIG. 18 is a sectional view taken along line XVIII-XVIII of FIG.6.

[0035]FIG. 19 is a sectional view taken along line XIX-XIX of FIG. 6.

[0036]FIG. 20 is a sectional view taken along line XX-XX of FIG. 7.

[0037]FIG. 21 is a sectional view taken along line XXI-XXI of FIG. 7.

[0038]FIG. 22 is an enlarged view of a part of FIG. 9.

[0039]FIG. 23 is a sectional view taken along line XXIII-XXIII of FIG.10.

[0040]FIG. 24 is a sectional view taken along line XXIV-XXIV of FIG. 12.

[0041]FIG. 25 is a sectional view taken along line XXV-XXV of FIG. 22.

[0042]FIG. 26 is a plan view, as viewed from above, of the shape of thebottom surface of a cylinder block of the present invention.

[0043]FIG. 27 is a sectional view taken along line XXVII-XXVII of FIG.26.

[0044]FIG. 28 is a sectional view taken along line XXVIII-XXVIII of FIG.27.

[0045]FIG. 29 is a top view of the cylinder block of the presentinvention.

[0046]FIG. 30 is a plan view, as viewed from above, of the shape of thebottom surface of a cylinder head of the present invention.

[0047]FIG. 31 is a top view of the cylinder head of the presentinvention.

[0048]FIG. 32 is a front view of a lubricating oil pump of the presentinvention.

[0049]FIG. 33 is a sectional view taken along line XXXIII-XXXIII of FIG.32.

[0050]FIG. 34 is an illustration of the outline of a lubricating oilcircuit according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0051] Now, an embodiment of a power unit for a vehicle with an internalcombustion engine 1 according to the present invention shown in thedrawings will be described. In this embodiment, the upward and downwarddirections mean the upward and downward directions with respect to thevehicle body, the front side means the front side with respect to thevehicle body, the rear side means the rear side with respect to thevehicle body, and the left and right mean the left and right as viewedfrom a person directed toward the front side.

[0052] Overall Structure

[0053] As shown in FIG. 1, in an off-road four-wheel vehicle 0 on whichthe power unit for vehicle with internal combustion engine 1 is mounted,pairs of front wheels 3 and rear wheels 4 are disposed respectively atfront and rear portions of a vehicle body frame 2, the front end rearends of transmission shafts directed in the forward and rearwarddirections from the power unit for vehicle with internal combustionengine 1 are connected to the front wheel 3 and the rear wheel 4 throughdifferential devices (not shown) and a front axle 6 and a rear axle 7,respectively, and the four-wheel vehicle 0 can run in a four-wheel drivemode by the power from the power unit 1.

[0054] In addition, the four-wheel vehicle 0 includes a bar handle 8 ata central portion in the width direction on the front side, a steeringmechanism 10 is provided at the lower end of a steering shaft 9connected to the bar handle 8, and a swiveling operation on the barhandle 8 is transmitted to the front wheels 3 through the steering shaft9 and the steering mechanism 10, whereby the four-wheel vehicle 0 can beturned to the left or the right.

[0055] Further, a fuel tank 11 is mounted on the vehicle body frame 2while being located on the upper side of the power unit 1, a seat 12 ismounted on the rear side thereof, a fan 13 and an oil cooler 14 aresequentially disposed on the front side of the power unit 1, acarburetor 15 and an air cleaner 16 are sequentially disposed on therear side of the power unit for vehicle with internal combustion engine1, and the front axle 6 and the rear axle 7 are supported on the vehiclebody frame 2 through shock absorbers 17.

[0056] Furthermore, as shown in FIGS. 2, 3 and 4, the power unit 1includes a 4-stroke-cycle internal combustion engine 20, a static oilhydraulic type non-stage transmission 100, and a speed change driveshaft controller 150. The 4-stroke-cycle internal combustion engine 20is an overhead-valve push-rod type single-cylinder internal combustionengine having a cylinder center axis in the vertical direction withrespect to the front-rear direction, as shown in FIG. 1, and slightlyinclined from the vertical direction to the left, as viewed forwardsfrom the rear side of the vehicle body, with respect to the left-rightdirection, as shown in FIG. 3. As shown in FIGS. 4 and 5, the static oilhydraulic type non-stage transmission 100 is a transmission in which aswash plate type oil hydraulic pump 110 and a swash plate type oilhydraulic motor 130 are disposed on the same axis in the front-reardirection and which changes the speed of rotation from a crankshaft 28of the 4-stroke-cycle internal combustion engine 20. The speed changedrive shaft controller 150 includes a speed change drive shaft 151 forreciprocating a drive member 152 for changing the swash plate angle ofthe swash plate type oil hydraulic pump of the swash plate type oilhydraulic motor 130.

[0057] In addition, in the 4-stroke-cycle internal combustion engine 20,as shown in FIGS. 1 and 4, a crankcase is partitioned into fourportions, namely, into a front case cover 21, a front crankcase 22, arear crankcase 23 and a rear case cover 24 in the front-rear direction,with vertical planes directed in the vehicle width direction as fayingsurfaces, a cylinder block 25, a cylinder head 26 and a head cover 27are sequentially stacked on the upper side of the front crankcase 22 andthe rear crankcase 23 at the center in the front-rear direction, and thefront case cover 21, the front crankcase 22, the rear crankcase 23, therear case cover 24, the cylinder block 25, the cylinder head 26 and thehead cover 27 are mutually integrally connected by bolts and the likewhich are not shown.

[0058] Further, as shown in FIG. 3 (the many-dotted portion in thefigure means a faying surface between one member and another), thecrankshaft 28 is rotatably borne on the front crankcase 22 and the rearcrankcase 23 while being directed in the front-rear direction (see FIG.4), and a piston 30 is slidably fitted in a cylinder bore 29 in thecylinder block 25 directed roughly in the vertical direction. The upperand lower ends of a connecting rod 31 are rotatably fitted on a pistonpin 30 a inserted in the piston 30 and a crank pin 28 a on thecrankshaft 28, and the crank shaft 28 is driven to rotate by thepressure of a combustion gas generated by the combustion of a mixturegas that is sucked into a combustion chamber 32 surrounded by thecylinder bore 29, the cylinder head 26 and the piston 30.

[0059] Furthermore, the cylinder head 26 is provided with an intake port33 opened rearwards and an exhaust port 34 opened forwards, and isprovided with an intake valve 35 and an exhaust valve 36 for openablyclosing the ports of the intake port 33 and the exhaust port 34 on theside of the combustion chamber 32, respectively. The carburetor 15 andthe air cleaner 16 (see FIG. 1) are connected to a rear opening portionof the intake port 33, whereas an exhaust gas clarifier, a muffler andthe like, which are not shown, are connected to a front opening portionof the exhaust port 34 through an exhaust pipe 18. As shown in FIG. 3, aspark plug 39 is screwed to the cylinder head 26 so that an electrodeportion 39 a of the spark plug 39 faces the combustion chamber 32.

[0060] The cylinder block 25 and the cylinder head 26 are provided withcooling fins 37 and cooling fins 38, respectively. A running airflowarising from the running of the vehicle and a cooling airflow generatedby a fan 13 come into contact with the cooling fins 37 and 38, wherebythe 4-stroke-cycle internal combustion engine 20 is cooled. Also, aswill be described later, the 4-stroke-cycle internal combustion engine20 is cooled by a cooling lubricating oil that passes inside thecylinder block 25 and the cylinder head 26.

[0061] In addition, as shown in FIG. 3, in the cylinder block 25 and thecylinder head 26, a communication hole 40 is formed on the right side ofthe cylinder bore 29 and substantially in parallel to the cylinder bore29, and a circular guide hole 41 is formed in top walls of the frontcrankcase 22 and the rear crankcase 23 at a position directly below thecommunication hole 40. At a position on the downward extension of thecommunication hole 40 and the guide hole 41, a camshaft 43 is rotatablyborne on camshaft pivot holes 67 c and 71 c provided in partition walls67 and 71 of the front crankcase 22 and the rear crankcase 23. A valvelifter 45 slidably fitted in the guide hole 41 is brought into contactwith a cam 44 on the camshaft 43. A front-rear pair of rocker arms 46are oscillatably borne on the cylinder head 26, with rocker shafts 42shown in FIG. 4 therebetween, in parallel to contact surfaces betweenthe cylinder block 25, the cylinder head 26 and the head cover 27. Apush rod 47 is interposed between one end portion of the rocker arm 46and the valve lifter 45, and the other end portion of the rocker arm 46is brought into contact with the top end of the intake valve 35 or theexhaust valve 36. In each of the intake valve 35 and the exhaust valve36, a valve spring 49 is interposed between a valve spring retainer 48mounted on the top end and a spring receiving portion 26 a of thecylinder head 26. A chain which is not shown is set around a drivesprocket 50 (see FIG. 4) fitted on the crankshaft 28 and a drivensprocket (not shown) fitted on the camshaft 43 and having a number ofteeth of two times that of the drive sprocket 50. When the crankshaft 28is rotated, the camshaft 43 is driven to rotate in a ratio of onerevolution to two revolutions of the crankshaft 28, and the intake valve35 and the exhaust valve 36 are opened and closed one time eachcorresponding to two revolutions of the crankshaft 28, with the samevalve timing as that in an ordinary 4-stroke-cycle internal combustionengine.

[0062] As shown in FIG. 4, at a rear portion of the crankshaft 28, abalancer drive gear 51 is integrally mounted to the crankshaft 28 at aposition on the rear side of the drive sprocket 50. As shown in FIG. 3,a balancer gear 52 meshed with the balancer drive gear 51 is borne onthe front crankcase 22 and the rear crankcase 23 through a balancershaft 53 at a position on the right side of the crankshaft 28. Further,an ACG 54 (AC generator) is disposed on the rear side of the balancerdrive gear 51, a rotor 54 a of the ACG 54 is fitted in the vicinity of arear end portion of the crankshaft 28, a recoil starter 55 is providedat a rear end portion of the crankshaft 28 on the rear side of the rotor54 a, a pump drive gear 56 is integrally mounted to a front portion ofthe crankshaft 28, and a starting clutch 57 is provided at the front endof the crankshaft 28 at a position on the front side of the pump drivegear 56.

[0063] Further, as shown in FIG. 4, a drive gear 58 is integrallyattached to a clutch outer 57 a, which is an output member of thestarting clutch 57. As shown in FIGS. 3 and 4, the static oil hydraulictype non-stage transmission 100, located slightly on the upper side andon the left side of the crankshaft 28, is disposed inside the frontcrankcase 22 and the rear crankcase 23. As shown in FIG. 5, an oilhydraulic motor rotary shaft 131 of the swash plate type oil hydraulicmotor 130 in the static oil hydraulic type non-stage transmission 100 isrotatably borne on the front case cover 21 and the rear crankcase 23. Amotor casing 132 of the swash plate type oil hydraulic motor 130 isrotatably borne on the oil hydraulic motor rotary shaft 131. A drivengear 101 is integrally attached to a pump casing 111 of the swash platetype oil hydraulic pump 110 rotatably borne on the oil hydraulic motorrotary shaft 131. As shown in FIG. 4, the driven gear 101 is meshed withthe drive gear 58 of the starting clutch 57. When the drive gear 58 ofthe starting clutch 57 is rotated, the pump casing 111 of the swashplate type oil hydraulic pump 110 in the static oil hydraulic typenon-stage transmission 100 is driven to rotate, with the oil hydraulicmotor rotary shaft 131 as a center.

[0064] In addition, as shown in FIG. 4, a gear transmission 160 isdisposed in the space surrounded by the rear crankcase 23 and the rearcase cover 24, and a main shaft 161 of the gear transmission 160 isspline-fitted to the oil hydraulic motor rotary shaft 131 of the staticoil hydraulic type non-stage transmission 100. As shown in FIG. 3, acounter shaft 162 is disposed at a position on the left lower side ofthe main shaft 161, and, further, an output shaft 163 is disposed at aposition on the right lower side of the counter shaft 162 and the mainshaft 161. The main shaft 161, the counter shaft 162 and the outputshaft 163 are rotatably borne on the rear crankcase 23 and the rear casecover 24. A counter gear 166, normally in mesh with a main gear 165integral with the main shaft 161, is rotatably mounted on the countershaft 162, and a shifter 167 is mounted on the counter shaft 162 so thatit cannot rotate but can axially slide in relation to the counter shaft162. A counter output gear 168 integral with the counter shaft 162 and agear 169 integral with the output shaft 163 mesh with each other. Whenthe shifter 167 slides forwards by a change-over mechanism (not shown)so as to engage with the counter gear 166, the counter gear 166 and thecounter shaft 162 are connected to each other, whereby the rotatingforce of the main shaft 161 is transmitted to the output shaft 163.

[0065] Moreover, as shown in FIG. 4, a reverse counter gear 170, locatedbetween the shifter 167 and the counter output gear 168, is rotatablymounted to the counter shaft 162. As shown in FIG. 3, a reverse shaft164 located adjacent to the main shaft 161 and the counter shaft 162 isrotatably borne on the rear crankcase 23 and the rear case cover 24 (seeFIG. 4), an input gear 171 on one side which is integral with thereverse shaft 164 is meshed with the main gear 165 on the main shaft161, and an output gear 172 on the other side which is integral with thereverse shaft 164 is meshed with the reverse counter gear 170 on thecounter shaft 162. When the shifter 167 slides rearwards, the counteroutput gear 168 and the counter shaft 162 are connected to each other,whereby the rotating force of the main shaft 161 is transmitted, in areverse rotating condition, to the output shaft 163 through the reverseshaft 164 and the counter shaft 162.

[0066] Both the front and rear ends of the output shaft 163 areconnected respectively to the transmission shafts 5 disposed on thefront and rear sides of the power unit 1, so that the rotating force ofthe output shaft 163 is transmitted to the front wheels 3 and the rearwheels 4 through the transmission shafts 5 and through the front axle 6and the rear axle 7.

[0067] In addition, as shown in FIG. 3, the speed change drive shaftcontroller 150 is disposed on the upper left side of the power unit 1,and the angle α between a plane connecting the center line of the speedchange drive gear 151 of the speed change drive shaft controller 150 andthe center line of the oil hydraulic motor rotary shaft 131 of thestatic oil hydraulic type non-stage transmission 100 and the center lineof the cylinder bore 29 of the 4-stroke-cycle internal combustion engine20 is as extremely small as about 10°.

[0068] Further, as shown in FIGS. 3 and 4, the speed change drive shaft151 of the speed change drive shaft controller 150 is provided with amale screw at a central portion in the longitudinal direction thereof,and the drive member 152 is meshed with the speed change drive shaft 151of the male screw. As shown in FIG. 5, the drive member 152 isoscillatably connected to arm portions 134, which project in a forkedform from a motor swash plate 133 of the swash plate type oil hydraulicmotor 130 in the static oil hydraulic type non-stage transmission 100,through a pin 135. As shown in FIG. 5, a gear 153 integral with thespeed change drive shaft 151 is meshed with a small gear 155 of a speedreduction gear 154, and a large gear 156 of the speed reduction gear 154is meshed with a pinion gear 159 integral with a rotary shaft 158 of acontrol motor 157. By the normal and reverse rotations of the controlmotor 157, the drive member is driven forwards and rearwards, wherebythe inclination angle of the motor casing 132 of the swash plate typeoil hydraulic motor 130 is controlled.

[0069] Furthermore, as shown in FIG. 3, along a plane orthogonal to theplane connecting the speed change drive shaft 151 of the speed changedrive shaft controller 150 and the oil hydraulic motor rotary shaft 131of the swash plate type oil hydraulic motor 130, a speed change ratiosensor 102 is disposed at a position on the left side of the swash platetype oil hydraulic motor 30.

[0070] Lubricating Oil Pump

[0071] Next, a lubricating oil pump 60 will be described.

[0072] As shown in FIGS. 6 and 7, which are views as viewed rearwardsfrom the front side of the front case cover 21 and the front crankcase22, and in FIG. 4, which is a sectional view taken along a verticalplane in the front-rear direction, the lubricating oil pump 60 isintegrally attached to the front case cover 21 and the front crankcase22 so that the front and rear surfaces of the lubricating oil pump 60make close contact with the rear surface of the front case cover 21 andthe front surface of the front crankcase 22, respectively. As shown inthe enlarged views of FIGS. 32 and 33, the lubricating oil pump 60includes of a trochoid type recovery pump 61 and a supply pump 62 whichare arranged on the same pump rotary shaft 63. The recovery pump 61 andthe supply pump 62 include inner rotors 61 a, 62 a mounted to the pumprotary shaft 63, outer rotors 61 b, 62 b meshed with the inner rotors 61a, 62 a, and pump bodies 61 c, 62 c rotatably enclosing the outer rotors61 b, 62 b, respectively. The outer rotors 61 b, 62 b are eccentricrelative to the inner rotors 61 a, 62 a, and the numbers of teeth of theouter rotors 61 b, 62 b are greater than the numbers of teeth of theinner rotors 61 a, 62 a by one.

[0073] As shown in FIG. 4, a pump gear 63 a integrally attached to thepump rotary shaft 63 of the lubricating oil pump 60 is meshed with apump drive gear 56 integral with the crankshaft 28. Attendant on therotation of the crankshaft 28, the pump rotary shaft 63 is driven torotate, whereby in the recovery pump 61 the lubricating oil is sucked inthrough a suction port 61 d and discharged through a discharge port 61e, and in the supply pump 62 the lubricating oil is sucked in through asuction port 62 d and discharged through a discharge port 62 e.

[0074] Crankcase

[0075] The specific structures of the front case cover 21, the frontcrankcase 22, the rear crankcase 23 and the rear case cover 24constituting the crankcase of the 4-stroke-cycle internal combustionengine 20 will be described.

[0076] As shown in FIGS. 4 and 6, the front case cover 21 is providedintegrally with a filter case 65 of the oil filter 64, and a filterelement 66 (see FIG. 4) is contained in the filter case 65. Thelubricating oil flowing into the filter case 65 through an inflowpassage 65 a at an outer circumferential portion of the filter case 65is filtered by the filter element 66, and is then discharged into acentral oil passage 65 b.

[0077] In addition, as shown in FIGS. 7 and 8, the front crankcase 22 isprovided integrally with a partition wall 67 parallel to the front andrear faying surfaces of the front crankcase 22, substantially at thecenter in the front-rear and width directions. The partition wall 67 isprovided with the following. A crankshaft hole 67 a for passing thecrankcase 28 therethrough. A transmission loose-fitting hole 67 b forloose fitting therein of the static oil hydraulic type non-stagetransmission 100 at a position on the left side in the crankcase. Acamshaft hole 67 c for passing and supporting the camshaft 43 therein. Abalancer shaft hole 67 d for passing and supporting the balancer shaft53 threin at a position on the lower side of the camshaft hole 67 c. Aspeed change drive shaft hole 67 e for passing the speed change driveshaft 151 of the speed change drive shaft controller 150 therethroughand an output shaft hole 67 f for passing and supporting the outputshaft 163 therein, at positions on the upper and lower sides of thetransmission loose fitting hole 67 b. A crank chamber communication hole67 g and a recovery pump suction communication hole 67 h incommunication with the suction port 61 d of the recovery pump 61, whichare located on the lower side of the counter shaft hole 67 f. A supplypump suction communication hole 67 i in communication with the suctionport 62 d of the supply pump 62, and a strainer lower lubricating oilsump 67 j ranging leftwards from the position directly below therecovery pump suction communication hole 67 h.

[0078] Further, as shown in FIG. 7, in the front crankcase 22, a tankpartition wall 68 projected forwards beyond the partition wall 67 isprovided at a required spacing along a right side wall 22 a (on the leftside in FIG. 7) of the front crankcase 22. As shown in FIG. 8, a tankpartition wall 69 projected rearwards beyond the partition wall 67 isprovided at a position different from that of the tank partition wall 68but substantially along the tank partition wall 68. A crank chamber 59and an oil tank chamber 70 are partitioned by the tank partition wall 68and the tank partition wall 69, and the partition wall 67 is providedwith tank communication holes 67 k (at four locations) at positions onthe right outer side of the tank partition wall 68 and the tankpartition wall 69 (the partition wall 67 is provided with only theseholes).

[0079] Furthermore, as shown in FIG. 8, the tank partition wall 69projected rearwards beyond the partition wall 67 is provided with acutout 69 b in an extension portion 69 a extended to the right upperside at a slant (left upper side at a slant in FIG. 8) of the portionpartitioning the crank chamber 59 and the oil tank chamber 70 so thatthe lubricating oil dwelling on the upper surface of the tank partitionwall 69 flows downwards through the cutout 69 b to be led to thestrainer lower lubricating oil sump 67 j.

[0080] The front crankcase 22 is provided with mount holes 22 b in bothlower side portions thereof. Rod-like members (not shown) penetratingthrough the mount holes 22 b and mount holes 23 b formed in both lowerside portions of the rear crankcase 23 are integrally mounted to thevehicle body frame 2 through rubber bushes (not shown).

[0081] In addition, as shown in FIGS. 9 and 10, like the front crankcase22, the rear crankcase 23 is integrally provided with a partition wall71 parallel to the front and rear faying surfaces of the rear crankcase23, at the center in the front-rear and width directions thereof. Thepartition wall 71 is provided with the following. A crankshaft hole 71 afor passing the crankshaft 28 therethrough. An oil hydraulic motorrotary shaft hole 71 b for rotatably bearing the oil hydraulic motorrotary shaft 131 of the swash plate type oil hydraulic motor 130 in thestatic oil hydraulic type non-stage transmission 100. A camshaft hole 71c for passing and supporting the camshaft 43 therein. A balancer shafthole 71 d for passing and supporting the balancer shaft 53 therein at aposition on the lower side of the camshaft hole 71 c. A counter shafthole 71 e for passing and supporting the counter shaft 162 therein at aposition intermediate between the main shaft 161 and the output shaft163 and on the left side. An output shaft hole 71 f for passing andsupporting the output shaft 163 therein at a position on the lower sideof the oil hydraulic motor rotary shaft hole 71 b. A crank chambercommunication hole 71 g at a position on the slanted right lower side ofthe output shaft hole 71 f. A reverse shaft hole 71 m (shown in FIG. 10only) for supporting the reverse shaft 164 at a position intermediatebetween the main shaft 161 and the output shaft 163 and on the rightside.

[0082] As shown in FIG. 9, the rear crankcase 23 is provided with astrainer lower lubricating oil sump 71 j in communication with thestrainer lower lubricating oil sump 67 j of the crankcase 22, and isprovided with a communication portion 71 h in communication with therecovery pump suction communication hole 67 h at a position on the upperside of the strainer lower lubricating oil sump 71 j. A strainer 85 isfitted in both side cutouts 71 l between the strainer lower lubricatingoil sump 71 j and the communication portion 71 h.

[0083] Further, as shown in FIG. 9, the rear crankcase 23 is providedwith a tank partition wall 72 (the tip end surface of the tank partitionwall 72 can make contact with the rear end surface of the tank partitionwall 69 of the front crankcase 22) projected forwards beyond thepartition wall 71 at a required spacing along a right side wall 23 a (onthe left side in FIG. 9) of the rear crankcase 23, and, as shown in FIG.10, the rear crankcase 23 is provided with a tank partition wall 73projected rearwards beyond the partition wall 71 at a position differentfrom the tank partition wall 72 but substantially along the tankpartition wall 72 so that the crank chamber 59 and the oil tank chamber70 are partitioned by the tank partition wall 72 and 73. The partitionwall 71 is provided with tank communication holes 71 k (at sixlocations) at positions on the right outer side of the tank partitionwall 72 and the tank partition wall 73. As shown in FIG. 10, an upperend portion 73 a of the tank partition wall 73 and a top wall portion 23c of the rear crankcase 23 are not connected to each other but areseparated from each other, so that a gap 73 b is formed between theupper end portion 73 a of the tank partition wall 73 and the top wallportion 23 c of the rear crankcase 23.

[0084] As shown in FIG. 9, the tank partition wall 72 projected forwardsbeyond the partition wall 71 is provided with a cutout 72 b in itsextension portion 72 a curvedly extended to the right upper side at aslant so that the lubricating oil dwelling on the upper surface of thetank partition wall 72 flows downwards through the cutout 72 b to be ledto the strainer lower lubricating oil sump 71 j.

[0085] Furthermore, as shown in FIG. 10, at a rear portion of the rearcrankcase 23, an overflow oil passage wall 74 projected rearwards fromthe rear surface of the partition wall 71 is extended downwards from thetop wall portion 23 c of the rear crankcase 23 so that a requiredspacing is present at a position on the upper left side of the tankpartition wall 73. The lower front end 74 a of the overflow oil passagewall 74 is extended to the crank chamber communication hole 71 g of thepartition wall 71, and an overflow oil passage 75 is constituted of thetank partition wall 73 and the overflow oil passage wall 74.

[0086] As shown in FIGS. 3 and 5, a breather chamber 80 is disposed onthe center axis of the speed change drive shaft 151 of the speed changedrive shaft controller 150. As shown in FIGS. 5, 9, 23 and 25, thepartition wall 71 is not present at a left upper portion (a right upperportion in FIG. 9) of the rear crankcase 23 corresponding to thebreather chamber 80, and a breather chamber bottom wall 76 flush withthe rear faying surface of the rear crankcase 23 is provided there. Abreather partition portion 77 for partitioning the breather chamber 80is projected forwards from the breather chamber bottom wall 76, and thebreather partition portion 77 is provided with a cutout portion 77 a asshown in FIG. 25.

[0087] In addition, a shaft support portion 76 a projected forwards froma substantially central portion of the breather chamber bottom wall 76is provided with a threaded hole 76 b. An outer circumferential edgeportion 78 b of a top wall 78 a of a breather cover 78, L-shaped insection as shown in FIG. 5, is brought into contact with an innercircumferential step portion 23 e of a left top wall 23 d of the rearcrankcase 23, as shown in FIG. 23. A bolt 79 penetrating through a holeformed at a central recessed portion 78 c of the top wall 78 a of thebreather cover 78 is screwed into the threaded hole 76 b in the shaftsupport portion 76 a so that the breather chamber 80 is constituted ofthe left top wall 23 d of the rear crankcase 23, the breather chamberbottom wall 76, the breather partition portion 77 and a bent wall 78 dof the breather cover 78.

[0088] Further, the breather chamber bottom wall 76 is provided with anopening 76 b. As shown in FIG. 5, one end of a breather pipe 81 isfitted in the opening 76 b, and the other end of the breather pipe 81 isconnected to an intake system of the 4-stroke-cycle internal combustionengine 20 through a pipe, a hose and the like which are not shown.

[0089] Furthermore, a tank partition wall 82 and an overflow oil passagewall 83 (shown in FIG. 11) whose tip end surfaces can make contact withthe rear end surfaces of the tank partition wall 73 and the overflow oilpassage wall 74 projected rearwards beyond the partition wall 71 of therear crankcase 23 (shown in FIG. 10) are projected forwards at the frontsurface of the rear case cover 24, as shown in FIG. 11.

[0090] The rear case cover 24 is provided with an opening 24 a in whichthe ACG 54 can be fitted, and, as shown in FIG. 12, a contact portion 24b with which the casing 54 b of the ACG 54 can make contact is formed atan outer circumferential rear surface of the opening 24 a.

[0091] Cylinder Block, Cylinder Head

[0092]FIG. 13 is a plan view in which the rear surface of the frontcrankcase 22 and the front surface of the rear crankcase 23 are laid oneach other. Under the condition where an opening 25 p of thecommunication hole 40 in the cylinder block 25 shown in FIG. 26coincides with openings 22 p and 23 p formed in the front crankcase 22and the rear crankcase 23. A cylinder bottom portion faying surface 25 xof the cylinder block 25 is laid on cylinder block faying surfaces 22 xand 23 x of the front crankcase 22 and the rear crankcase 23. Cylindersleeve insertion holes 22 r and 23 r are composed of semi-circularcutouts in the top walls of the front crankcase 22 and the rearcrankcase 23, and a cylinder sleeve 25 r (see FIG. 4) of the cylinderblock 25 is fitted in the cylinder sleeve insertion holes 22 r and 23 r.

[0093] In addition, FIG. 29 is a top view of the cylinder block 25.Under the condition where an opening 26 p of the communication hole 40in the cylinder head 26 shown in FIG. 30 coincides with the opening 25 pof the communication hole 40 in the cylinder block 25, a cylinder headbottom portion faying surface 26 y of the cylinder head 26 is laid on acylinder head faying surface 25 y of the cylinder block 25, and lowerend screws of four bolts (not shown) penetrating through bolt holes 26 aand 25 a formed in the cylinder head 26 and the cylinder block 25 arescrewed into bolt holes 22 q and 23 q respectively formed in the frontcrank case 22 and the rear crankcase 23, whereby the cylinder block 25,the cylinder head 26, the front crankcase 22 and the rear crankcase 23are mutually integrally connected.

[0094] Further, as shown in FIG. 3, the outer circumferential surface ofthe head cover 27 is brought into contact with the top surface of thecylinder head 26, and the head cover 27 is integrally connected to thecylinder head 26 by bolts or the like, which are not shown.

[0095] Lubricating Oil Circuit

[0096] Referring to FIG. 34, in this embodiment, the outline of alubricating oil circuit through which the lubricating oil in the4-stroke-cycle internal combustion engine 20 is supplied to individualportions of the power unit 1 will be described. The suction port 61 d ofthe recovery pump 61 is connected to the crank chamber 59 through thestrainer 85, the discharge port 61 e of the recovery pump 61 isconnected to a suction port 14 a of the oil cooler 14, and a dischargeport 14 b of the oil cooler 14 is connected to the ACG 54, the cylinderblock 25 and the cylinder head 26 and is connected to the oil tankchamber 70.

[0097] The suction port 62 d of the supply pump 62 is connected to abottom portion of the oil tank chamber 70, the discharge port 62 e ofthe supply pump 62 is connected to the suction port 65 a of the oilfilter 64, and the discharge port 65 b of the oil filter 64 is connectedto the static oil hydraulic type non-stage transmission 100, the4-stroke-cycle internal combustion engine 20 and the starting clutch 57.

[0098] Further, the discharge ports 61 e and 62 e of the recovery pump61 and the supply pump 62 are connected to the crank chamber 59 and theoil tank chamber 70 through relief valves 86 and 87, respectively.

[0099] Next, the crank chamber 59 and the oil tank chamber 70,integrally constituted inside the front case cover 21, the frontcrankcase 22, the rear crankcase 23 and the rear case cover 24, arepartitioned by the partition wall 67 of the front crankcase 22 intofront and rear portions. In the front portion, the crank chamber 59 andthe oil tank chamber 70 are partitioned into left and right portions bythe tank partition wall 68 of the front crankcase 22 (shown in FIG. 7)and a tank partition wall 89 formed of the front case cover 21correspondingly to the tank partition wall 68. In a central portion inthe front-rear direction intermediately bound between the partition wall67 of the front crankcase 22 and the partition wall 71 of the rearcrankcase 23, the crank chamber 59 and the oil tank chamber 70 arepartitioned into left and right portions by the tank partition wall 69of the front crankcase 22 (shown in FIG. 8) and the tank partition wall72 of the rear crankcase 23 (shown in FIG. 9). The crank chamber 59 andthe oil tank chamber 70 are partitioned by the partition wall 71 of therear crankcase 23 into front and rear portions. At the rear portion, thecrank chamber 59 and the oil tank chamber 70 are partitioned into leftand right portions by the tank partition wall 73 (shown in FIG. 10) andthe tank partition wall 82 (shown in FIG. 11).

[0100] In addition, as shown in FIGS. 7 and 8, the crank chamber 59 atthe front portion and the crank chamber 59 at the central portion in thefront-rear direction are mutually communicated through the crank chambercommunication hole 67 g formed in the partition wall 67 of the frontcrankcase 22 and the strainer lower lubricating oil sump 67 j. As shownin FIGS. 9 and 10, the crank chamber 59 at the central portion in thefront-rear direction and the crank chamber 59 at the rear portion aremutually communicated through the crank chamber communication hole 71 gformed in the partition wall 71 of the rear crankcase 23 and thestrainer lower lubricating oil sump 71 j.

[0101] Further, as shown in FIGS. 7 and 8, the oil tank chamber 70 atthe front portion and the oil tank chamber 70 at the central portion inthe front-rear direction are mutually communicated through the tankcommunication holes 67 k (at four locations) formed in the partitionwall 67 of the front crankcase 22. As shown in FIGS. 9 and 10, the oiltank chamber 70 at the central portion in the front-rear direction andthe oil tank chamber 70 at the rear portion are mutually communicatedthrough the tank communication holes 71 k (at six locations) formed inthe partition wall 71 of the rear crankcase 23.

[0102] Oil passages formed inside the front case cover 21, the frontcrankcase 22, the rear crankcase 23, the rear case cover 24, thecylinder block 25 and the cylinder head 26 will be describedspecifically, according to the lubricating oil circuit shown in FIG. 34.

[0103] As shown in FIGS. 6 and 7, the suction port 61 d of the recoverypump 61 is connected to the recovery pump suction communication hole 67h of the front crankcase 22. When the rotary shaft 63 of the lubricatingoil pump 60 is driven to rotate, the lubricating oil dwelling in thestrainer lower lubricating oil sumps 67 j and 71 j is filtered throughthe strainer 85 as shown in FIG. 9, and then flows through thecommunication portion 71 h of the rear crankcase 23 and the recoverypump suction communication hole 67 h of the front crankcase 22 into thesuction port 61 d of the recovery pump 61.

[0104] In addition, as shown in FIGS. 6 and 14, the discharge port 61 eof the recovery pump 61 is connected to an opening 21 a on the rear sideof the front case cover 21, the opening portion 21 a is in communicationwith a front end opening 21 c through a communication passage 21 bdirected forwards, and the opening 21 c and the inflow port 14 a of theoil cooler 14 are connected to each other through a hose, a pipe and thelike, which are not shown, so that the lubricating oil discharged fromthe discharge port 61 e of the recovery pump 61 is fed to the oil cooler14. As shown in FIG. 14, the branch passage 21 d is branched from thecommunication passage 21 b, and a relief valve 86 is interposed in thebranch passage 21 d. When the lubricating oil pressure in thecommunication passage 21 b reaches or exceeds a predetermined setpointpressure, the relief valve 86 operates so that the lubricating oil isreturned from the branch passage 21 d into the crank chamber 59 throughan opening 21 e.

[0105] Further, the discharge port 14 b of the oil cooler 14 isconnected to a return port 21 f of the front case cover 21 shown in FIG.6 through a hose, a pipe and the like, which are not shown. As shown inFIG. 15, the return port 21 f is in communication with an opening 21 hthrough a communication passage 21 g, and to the oil tank chamber 70through an orifice 21 i.

[0106] Furthermore, as shown in FIGS. 6 and 7, the opening 21 h of thefront case cover 21 and an opening 22 h of the front crankcase 22coincide with each other, and, as shown in FIG. 20, the opening 22 h isin communication with an opening 22 j through a communication passage 22i.

[0107] As shown in FIG. 13, the opening 22 j opened in the cylinderblock faying surface 22 x of the front crankcase 22 coincides with anopening 25 j opened in the cylinder bottom portion faying surface 25 xof the cylinder block 25 shown in FIG. 26. As shown in FIG. 27, theopening 25 j is in communication with an opening 25 l in the cylinderhead faying surface 25 y of the cylinder block 25 through a verticalcommunication passage 25 k. As shown in FIGS. 29 and 30, the opening 25l in the cylinder block 25 coincides with a communication passage 26 lin the cylinder head 26, and the upper end of the communication passage26 l is exposed into the space surrounded by the head cover 27.

[0108] As shown in FIGS. 26 and 27, the vertical communication passage25 k and a vertical communication passage 25 n parallel thereto aremutually communicated through a communication passage 25 m extending inthe front-rear direction, the upper end opening 25 o of the verticalcommunication passage 25 n coincides with an opening 26 o in thecylinder head 26, and the upper end of the opening 26 o is also exposedto the spacing surrounded by the head cover 27.

[0109] Further, the lower end opening 25 s of the vertical communicationpassage 25 n in the cylinder block 25 shown in FIG. 27 is incommunication with an opening 23 s in the rear crankcase 23 shown inFIG. 13. As shown in FIG. 22, the opening 23 s is in communication withan opening 23 u through a communication passage 23 t, and the opening 23u in the rear crankcase 23 is in communication with an opening 24 u inthe rear case cover 24 shown in FIG. 11. As shown in FIG. 24, theopening 24 u is in communication with an opening 24 w through acommunication passage 24 v, and the opening 24 w in the rear case cover24 is in communication with an ACG lubricating oil jet port (not shown)provided in a cover 54 b (see FIG. 4) of the ACG 54.

[0110] As has been described above, the lubricating oil fed to the oilcooler 14 by the recovery pump 61 and cooled by the oil cooler 14 is fedto the return port 21 f in the front case cover 21 shown in FIG. 15,passed through the communication passage 21 g, is jet into the oil tankchamber 70 through the orifice 21 i, and is allowed to dwell in the oiltank chamber 70. The lubricating oil dwelling in the oil tank chamber 70is sucked into the suction port 62 d of the supply pump 62 through thesupply pump suction communication hole 67 i opened into the oil tankchamber 70, and the pressure lubricating oil pressurized by the supplypump 62 is fed through the discharge port 62 e of the supply pump 62 toa discharge port 21 j in the front case cover 21, as shown in FIG. 16.

[0111] The discharge port 21 j in the front case cover 21 shown in FIG.16 is connected to the inflow passage 65 a in the filter case 65 of theoil filter 64. As shown in FIGS. 4 and 19, the discharge passage 65 b inthe filter case 65 is connected to a center hole 131 a in the oilhydraulic motor rotary shaft 131 of the static oil hydraulic typenon-stage transmission 100, and is connected to a center hole 68 b inthe crankshaft 28 through an orifice 65 c shown in FIGS. 4 and 19. Asshown in FIG. 4, the center hole 68 b is in communication with a clutchcommunication hole 68 c. Thus, the cooled lubricating oil filtered bythe oil filter 64 is supplied to the static oil hydraulic type non-stagetransmission 100 and the crankshaft 28.

[0112] In addition, as shown in FIG. 17, in the front case cover 21, arelief valve 87 is interposed in a communication passage 65 d betweenthe communication between a filter chamber in the filter case 65 and thecrank chamber 59 (the left side in the figure). As shown in FIG. 18, abranch passage 65 e is branched from a discharge passage 65 b in thefilter case 65, a check valve 88 is interposed in the branch passage 65e, and a lubricating oil jet port 65 f is formed from the branch passage65 e toward the starting clutch 57 in the crank chamber 59. When thepressure inside the filter chamber in the filter case 65 exceeds apredetermined value, the lubricating oil is ejected into the crankchamber 59 through the relief valve 87. In addition, when thelubricating oil pressure inside the discharge passage 65 b in the filtercase 65 exceeds a predetermined value, the lubricating oil is ejectedinto the crank chamber 59 through the check valve 88. Further, thelubricating oil in the discharge passage 65 b in the filter case 65 isjetted through the lubricating oil jet port 65 f toward the startingclutch 57.

[0113] Since the embodiment shown in the drawings is constituted asdescribed above, when the 4-stroke-cycle internal combustion engine 20is started by operating the recoil starter 55 in the condition where thecounter gear 166 and the counter shaft 162 are connected to each otherby moving the shifter 167 forwards, the 4-stroke-cycle internalcombustion engine 20 is put into an operating condition. When therotational frequency of the crankshaft 28 exceeds a predeterminedrotational frequency, the starting clutch 57 is put into a connectedcondition, and the pump casing 111 of the static oil hydraulic typenon-stage transmission 100 is driven to rotate.

[0114] The oil hydraulic motor rotary shaft 131 is driven to rotate at arequired speed change ratio according to the magnitude of theinclination angle of the motor swash plate 133 of the swash plate typeoil hydraulic motor 130 set correspondingly to the axial position of thedrive member 152 in the speed change drive shaft controller 150, thespeed of the counter shaft 162 is reduced at a predetermined speedchange ratio at the gear transmission 160, and the power is transmittedfrom the output shaft 163 to the front wheels 3 and the rear wheels 4through the front and rear transmission shafts 5 and through the frontaxle 6 and the rear axle 7, whereby the four-wheel vehicle 0 can bemoved forwards.

[0115] In addition, as shown in FIG. 3, the angle a between the planeconnecting the swash plate type oil hydraulic pump 110 of the static oilhydraulic type non-stage transmission 100, the oil hydraulic motorrotary shaft 131 on the center line of the swash plate type oilhydraulic motor 130 and the speed change drive shaft 151 of the speedchange drive shaft controller 150 and the center line of the cylinderbore 29 is as small as about 10°. Besides, on the left side of the4-stroke-cycle internal combustion engine 20, the static oil hydraulictype non-stage transmission 100 and the speed change drive shaftcontroller 150 are disposed close to the 4-stroke-cycle internalcombustion engine 20. Therefore, the size in the width direction of thepower unit for vehicle with internal combustion engine 1 is small,providing a compact design, which improves the mountability of the powerunit on the four-wheel vehicle 0.

[0116] Further, since the speed change ratio sensor 102 is disposed onthe left outer side of the static oil hydraulic type non-stagetransmission 100, the maintenance, inspection and repair of the speedchange ratio sensor 102 can be easily carried out from the left side ofthe four-wheel vehicle 0.

[0117] Furthermore, the breather chamber 80 is located on the left upperside of the crank chamber 59 and disposed on the extension line of thespeed change drive shaft 151 of the speed change drive shaft controller150, and the static oil hydraulic type non-stage transmission 100 isdisposed on the lower side thereof. Therefore, the lubricating oildroplets scattered from the crankshaft 28 and the main gear 165, countergear 166, shifter 167, counter output gear 168 and gear 169 of the geartransmission 160 are shielded by the static oil hydraulic type non-stagetransmission 100, thereby being inhibited from reaching the left upperside of the crank chamber 59, and a blow-by gas with a low oil mistmixing ratio is introduced into the breather chamber 80. As a result,the breather chamber 80 may be small in capacity, and can be simplifiedin structure.

[0118] Moreover, since the crankshaft 28 is directed in the front-reardirection of the vehicle body, the ACG 54, the recoil starter 55, thestarting clutch 57 and the gear transmission 160 are arranged in thefront-rear direction of the vehicle body, which, in cooperation with thearrangement of the static oil hydraulic type non-stage transmission 100and the speed change drive shaft controller 150 close to the center axisof the cylinder bore 29, promises a further reduction of the size of thepower unit 1 and a further enhancement of the mountability thereof onthe four-wheel vehicle 0.

[0119] In addition, as shown in FIG. 3, the static oil hydraulic typenon-stage transmission 100 is disposed on the left side in the spaceinside the crankcase composed of the front case cover 21, the frontcrankcase 22, the rear crankcase 23 and the rear case cover 24, and theoil tank chamber 70 is disposed on the right side in the space insidethe crankcase. Therefore, it is easy to take the weight balance betweenthe left and right sides of the power unit 1 by utilizing the weight ofthe static oil hydraulic type non-stage transmission 100 and the weightof the lubricating oil in the oil tank chamber 70.

[0120] Further, as shown in FIG. 6, the tank partition wall 89 isintegrally projected from the inside wall surface of the front casecover 21. As shown in FIGS. 7 and 8, the tank partition wall 68 and thetank partition wall 69 are integrally projected forwards and rearwardsfrom the partition wall 67 of the front crankcase 22. As shown in FIGS.9 and 10, the tank partition wall 72 and the tank partition wall 73 areintegrally projected forwards and rearwards from the partition wall 71of the rear crankcase 23. As shown in FIG. 11, the tank partition wall82 is integrally projected rearwards from the inside wall surface of therear case cover 24. Therefore, there is no need for special componentparts for constituting the oil tank chamber 70, the weight and thenumber of working steps are reduced, and the crankcase can be reduced inweight and cost and enhanced in rigidity.

[0121] Furthermore, the oil tank chamber 70 is formed between the frontcrankcase 22 and the rear crankcase 23 by the tank partition wall 69(see FIG. 8) projected rearwards from the partition wall 67 of the frontcrankcase 22 and the tank partition wall 72 (see FIG. 9) projectedforwards from the partition wall 71 of the rear crankcase 23. The oiltank chamber 70 is formed between the front case cover 21 and the frontcrankcase 22 by the tank partition wall 89 (see FIG. 6) projectedrearwards from the inside wall surface of the front case cover 21 andthe tank partition wall 68 (see FIG. 7) projected forwards from thepartition wall 67 of the front crankcase 22. The oil tank chamber 70 isformed between the rear crankcase 23 and the rear case cover 24 by thetank partition wall 73 (see FIG. 10) projected rearwards from thepartition wall 71 of the rear crankcase 23 and the tank partition wall82 (see FIG. 11) projected forwards from the inside wall surface of therear case cover 24. Therefore, the capacity of the oil tank chamber 70is extremely large.

[0122] Moreover, since the front case cover 21, the front crankcase 22,the rear crankcase 23 and the rear cover case 24 can be die-cast orcast, a further enhancement of productivity and a further reduction incost can be achieved.

[0123] In addition, the recovery pump 61 by which the lubricating oildwelling in the strainer lower lubricating oil sumps 67 j and 71 j atbottom portions inside the crankcase is fed to the oil tank chamber 70and the supply pump 62 by which the lubricating oil is supplied from theoil tank chamber 70 to the crankshaft 28 and the starting clutch 57 ofthe 4-stroke-cycle internal combustion engine 20 and the static oilhydraulic non-stage transmission 100 are arranged coaxially. Therefore,the overall size of the lubricating oil pump 60 composed of the recoverypump 61 and the supply pump 62 is reduced, and the lubricating oil pump60 can be reduced in size and weight. Further, the oil passage betweenthe recovery pump 61 and the supply pump 62 and the oil passage betweenthe lubricating oil pump 60 and the oil tank chamber 70 are shortened,whereby the pump loss of the lubricating oil pump 60 is reduced.

[0124] Further, the filter case 65 of the oil filter 64 for filteringthe lubricating oil to be supplied from the oil tank chamber 70 to theindividual portions of the 4-stroke-cycle internal combustion engine 20and the static oil hydraulic type non-stage transmission 100 is arrangedat a position on the front side of the oil tank chamber 70 andoverlapping with the oil tank chamber 70 as viewed in the front-reardirection of the vehicle body. Therefore, the oil tank chamber 70 andthe oil filter 64 are arranged close to each other, and the lubricatingoil in the oil filter 64 is immediately returned into the oil tankchamber 70 through the relief valve 87 interposed in the communicationpassage 65 d of the oil filter 64, so that the pump loss of the supplypump 62 is low.

[0125] Furthermore, the oil filter 64 is located on the front side ofthe front case cover 21; therefore, as shown in FIG. 4, a cover 64 a ofthe oil filter 64 can be easily removed on the front side of thefour-wheel vehicle 0, replacement of the filter element 66 can be easilycarried out, and the maintenance, inspection and repair of the oilfilter 64 can be carried out quickly and easily.

[0126] In addition, as for the cylinder block 25, the cylinder head 26and the ACG 54, which do not need a filtered lubricating oil but need acooled lubricating oil, the lubricating oil cooled by passing throughthe oil cooler 14 is supplied directly to the cylinder block 25, thecylinder head 26 and the ACG 54 without passing through the oil filter64. Therefore, the load on the supply pump 62 can be reduced, the powerloss with respect to the supply pump 62 can be greatly reduced, and thesupply pump 62 can be reduced in size.

[0127] As shown in FIG. 15, the lubricating oil fed to the oil cooler 14by the recovery pump 61 and cooled by the oil cooler 14 flows throughthe return port 21 f of the front case cover 21 and the communicationpassage 21 g to reach the opening 21 h, and is fed from the opening 22 hof the front crankcase 22 shown in FIG. 20 to the opening 22 j throughthe communication passage 22 i. As shown in FIGS. 13, 26 and 27, thelubricating oil is fed from the opening 22 j of the front crankcase 22to the top surface opening 25 l of the cylinder block 25 through thebottom surface opening 25 j and the vertical communication passage 25 kin the cylinder block 25. Further, as shown in FIGS. 29, 30 and 31, thelubricating oil reaches the top opening 26 l of the cylinder head 26,flows out through the top surface opening 26 l to the top surface of thecylinder head 26, and drops from the cylinder head 26 back into thecrank chamber 59 through the communication hole 40, whereby the cylinderblock 25 and the cylinder head 26 are cooled.

[0128] In addition, as shown in FIG. 27, the communication passage 25 mis branched from the vertical communication passage 25 k. Therefore, apart of the lubricating oil rising through the vertical communicationpassage 25 k flows through the communication passage 25 m to reach thevertical communication passage 25 n, and the lubricating oil flowing inan upper portion of the vertical communication passage 25 n flows outthrough the top surface opening 26 o to the top surface of the cylinderhead 26 in the same manner as the lubricating oil flowing through thetop surface opening 26 l, and drops through the communication hole 40into the crank chamber 59, whereby the cylinder block 25 and thecylinder head 26 are cooled.

[0129] Further, the lubricating oil flowing in a lower portion of thevertical communication passage 25 n flows through the bottom surfaceopening 25 s of the cylinder block 25 to reach the opening 23 s in therear crankcase 23, is fed through the communication passage 23 t shownin FIG. 22 to the opening 23 u, is fed from the opening 23 u through theopening 24 u and the communication passage 24 v in the rear case cover24 shown in FIG. 24 to the opening 24 w, and is jetted through thelubricating oil jet port of the ACG 54, whereby the ACG 54 is cooled.

[0130] Further, the cooled lubricating oil sucked up from the crankchamber 59 to be supplied to the oil cooler 14 by the recovery pump 61and cooled by the oil cooler 14 is not supplied to the oil filter 64 butsupplied directly to the cylinder block 25 and the cylinder head 26.Therefore, the cylinder block 25 and the cylinder head 26 are not onlycooled by the air cooling, in which a cooling airflow blasted rearwardsby the fan 13 and a running airflow caused by running the vehicle arebrought into contact with the cooling fins 37 and the cooling fins 38,but also cooled by the lubricating oil cooling in which the cooledlubricating oil passes inside the cylinder block 25 and the cylinderhead 26. As a result, the cylinder block 25 and the cylinder head 26,and hence the portion surrounding the combustion chamber 32, are cooledsufficiently.

[0131] Furthermore, the lubricating oil cooled by the oil cooler 14 isalso supplied to the recoil starter 54 without passing through the oiltank chamber 70, so that the recoil starter 54 is also cooledsufficiently.

[0132] In addition, upper end edges 73 a and 82 a of the tank partitionwall 73 projected rearwards from the partition wall 71 (shown in FIG.10) and the tank partition wall 82 projected forwards from the insidewall surface (shown in FIG. 11) are located on the lower side of upperend edges 89 a and 68 a of the tank partition wall 89 projectedrearwards from the inside wall surface of the front cover case 21 (shownin FIG. 6) and the tank partition wall 68 projected forwards from thepartition wall 67 of the front crankcase 22 (shown in FIG. 7). Further,the partition wall 67 of the front crankcase 22 is provided with thetank communication hole 67 k, and the partition wall 71 of the rearcrankcase 23 is provided with the tank communication hole 71 k.Therefore, the oil surfaces of the lubricating oil in the oil tank 70are all maintained at the same level, and the lubricating oil in the oiltank chamber 70 can calmly flow into the overflow oil passage 75 and theoverflow oil passage 84 via the upper end edges 73 a and 82 a of thetank partition wall 73 and the tank partition wall 82 which are low inheight. As a result, the lubricating oil in the crank chamber 59 isprevented from being stirred by the crankshaft 28, whereby power lossand generation of mist of the lubricating oil are reduced. Also, thelubricating oil is led into the strainer lower lubricating oil sumps 67j and 71 j at the bottom portions of the crank chamber 59 smoothly andcalmly, whereby the generation of bubbles is also reduced.

[0133] Further, as shown in FIGS. 10 and 11, the overflow oil passages75 and 84 are constituted of the tank partition wall 73, the tankpartition wall 82 and overflow oil passage walls 74 and 83, which areformed integrally with the rear crankcase 23 and the rear case cover 24,respectively. Therefore, the overflow oil passages 75 and 84 areextremely simplified in structure, which reduces manufacturing costs.

[0134] Furthermore, the oil tank chamber 70 between the rear crankcase23 and the rear case cover 24 is formed in a crescent shape along theright side wall 23 a of the rear crankcase 23 (the right side wall ofthe rear case cover 24 is not denoted by any symbol). Therefore, thetank partition wall 73, the tank partition wall 82 and the overflow oilpassage walls 74 and 83 are also formed in similar shapes, so that thelubricating oil having flowed over partition wall upper edges 73 a and82 a of the oil tank chamber 70 is led to the strainer lower lubricatingoil sumps 67 j and 71 j at the bottom portions of the crank chamber 59,without generating a turbulent flow.

[0135] The present invention should not be considered limited to theparticular examples or materials described above, but rather should beunderstood to cover all aspect of the invention as fairly set out in theattached claims. Various modifications, equivalent processes, as well asnumerous structures to which the present invention may be applicablewill be readily apparent to those of skill in the art to which thepresent invention is directed upon review of the instant specification.

What is claimed is:
 1. A power unit for a vehicle with an internalcombustion engine comprising: an internal combustion engine having acrankshaft directed in a front-rear direction of a vehicle body; astatic oil hydraulic non-stage transmission comprised of a swash plateoil hydraulic pump and a swash plate oil hydraulic motor; and alubricating oil tank for holding a lubricating oil to be supplied toindividual portions of the internal combustion engine and to thetransmission, wherein the transmission is disposed on either the left orright side of the crankshaft, and the lubricating oil tank is formedintegrally with a main body of the power unit and is disposed on alateral side of the crankshaft that is opposite to the side on which thetransmission is disposed.
 2. The power unit for a vehicle with aninternal combustion engine as set forth in claim 1, wherein thelubricating tank is formed integrally with a main body of the internalcombustion engine.
 3. The power unit for a vehicle with an internalcombustion engine as set forth in claim 1, wherein the lubricating oiltank is formed over the range of a crankcase for bearing the crankshaftand a crankcase cover making contact with an outside surface of thecrankcase and covering the outside surface of the crankcase.
 4. Thepower unit for a vehicle with an internal combustion engine as set forthin claim 1, wherein an oil pump is disposed substantially directly belowthe crankshaft, and the oil pump comprises: a recovery pump by which alubricating oil dropped to a bottom portion of the inside of thecrankcase is returned to the lubricating oil tank; and a supply pump forsupplying the lubricating oil from the lubricating oil tank toindividual portions of the internal combustion engine and to thetransmission through an oil filter, the recovery pump and the supplypump being disposed coaxially.
 5. The power unit for a vehicle with aninternal combustion engine as set forth in claim 4, wherein the oilfilter is disposed at a position on a front side of the lubricating oiltank and overlapping with the lubricating oil tank as viewed forwardswith respect to the vehicle.
 6. The power unit for a vehicle with aninternal combustion engine as set forth in claim 2, wherein an oil pumpis disposed substantially directly below the crankshaft, and the oilpump comprises: a recovery pump by which a lubricating oil dropped to abottom portion of the inside of the crankcase is returned to thelubricating oil tank; and a supply pump for supplying the lubricatingoil from the lubricating oil tank to individual portions of the internalcombustion engine and to the transmission through an oil filter, therecovery pump and the supply pump being disposed coaxially.
 7. The powerunit for a vehicle with an internal combustion engine as set forth inclaim 6, wherein the oil filter is disposed at a position on the frontside of the lubricating oil tank and overlapping with the lubricatingoil tank as viewed forwards with respect to the vehicle.
 8. A power unitfor a vehicle with an internal combustion engine comprising: an internalcombustion engine having a crankshaft directed in a front-rear directionof a vehicle body; a static oil hydraulic non-stage transmissioncomprised of a swash plate oil hydraulic pump and a swash plate oilhydraulic motor; and tank means for holding a lubricating oil to besupplied to individual portions of the internal combustion engine and tothe transmission, wherein the transmission is disposed on either theleft or right side of the crankshaft, and the tank means is formedintegrally with a main body of the power unit and is disposed on alateral side of the crankshaft that is opposite to the side on which thetransmission is disposed.
 9. The power unit for a vehicle with aninternal combustion engine as set forth in claim 1, wherein the tankmeans is formed integrally with a main body of the internal combustionengine.
 10. The power unit for a vehicle with an internal combustionengine as set forth in claim 1, wherein the tank means is formed overthe range of a crankcase for bearing the crankshaft and a crankcasecover making contact with an outside surface of the crankcase andcovering the outside surface of the crankcase.
 11. The power unit for avehicle with an internal combustion engine as set forth in claim 8,wherein an oil pump is disposed substantially directly below thecrankshaft, and the oil pump comprises: recovery means for recoveringlubricating oil dropped to a bottom portion of the inside of thecrankcase and returning it to the tank means; and supply means forsupplying the lubricating oil from the tank means to individual portionsof the internal combustion engine and to the transmission through an oilfilter.
 12. The power unit for a vehicle with an internal combustionengine as set forth in claim 11, wherein the oil filter is disposed at aposition on a front side of the lubricating oil tank and overlappingwith the lubricating oil tank as viewed forwards with respect to thevehicle.
 13. The power unit for a vehicle with an internal combustionengine as set forth in claim 10, wherein an oil pump is disposedsubstantially directly below the crankshaft, and the oil pump comprises:recovery means for recovering lubricating oil dropped to a bottomportion of the inside of the crankcase and returning it to the tankmeans; and supply means for supplying the lubricating oil from thelubricating oil tank to individual portions of the internal combustionengine and to the transmission through an oil filter.
 14. The power unitfor a vehicle with an internal combustion engine as set forth in claim13, wherein the oil filter is disposed at a position on the front sideof the lubricating oil tank and overlapping with the lubricating oiltank as viewed forwards with respect to the vehicle.